Friday, February 03, 2006

Science Series: Viruses

Viruses straddle the definition of life. They lie somewhere between supra molecular complexes and very simple biological entities. Viruses contain some of the structures and exhibit some of the activities that are common to organic life, but they are missing many of the others. In general, viruses are entirely composed of a single strand of genetic information encased within a protein capsule. Viruses lack most of the internal structure and machinery which characterize 'life', including the biosynthetic machinery that is necessary for reproduction. In order for a virus to replicate it must infect a suitable host cell.

Viruses are the ultimate parasites. They are essentially "dead" until they find a host. Only then can they engage in their cycle of life. They rely on hosts to (re)produce their genetic code.

A virus makes use of existing host enzymes and other molecules of a host cell to create more virus particles (virions). . . . Viruses rely on host cell ribosomes for the production of viral proteins and utilize several distinct strategies to make the host cell synthesize the viral proteins. For example, at least some +RNA viruses use Internal Ribosome Entry Site (IRES) segments to drive the translation from their genomic +RNA molecule. Viruses are neither unicellular nor multicellular organisms; they are somewhere between being living and non-living. Viruses have genes and show inheritance, but are reliant on host cells to produce new generations of viruses. Many viruses have similarities to complex molecules. Because viruses are dependent on host cells for their replication they are generally not classified as "living". Whether or not they are "alive", they are obligate parasites, and have no form which can reproduce independently of their host. Like most parasites, they have a specific host range, sometimes specific to one species (or even limited cell types of one species) and sometimes more general.

This is not a machine; it's a bacteriophage virus. Perhaps just a highly efficient machine for genetic duplication?

Some theories hold that viruses, in mobilizing and mixing genetic information, are playing a role in the process of evolution too large and complex for us to grasp completely

It is a surprise to most who think of viruses simply as parasites that they make up the largest component of biomass on this planet . . . . So far every living organism that has been studied to date has had at least one virus associated with it, and viruses outnumber all other life forms by at least an order of magnitude . . . . When considering that not only is viral presence on this planet all encompassing, but every sequenced organism to date has a major component of its genome that is viral in origin, it becomes apparent that viruses are integral players in the evolution of what we presently consider life.

[B]ecause viruses can transfer genetic material between different species of host, they are extensively used in genetic engineering. Viruses also carry out natural "genetic engineering": a virus may incorporate some genetic material from its host as it is replicating, and transfer this genetic information to a new host, even to a host unrelated to the previous host. This is known as transduction, and in some cases it may serve as a means of evolutionary change -- although it is not clear how important an evolutionary mechanism transduction actually is.

It seems unclear whether viruses are the most primitive form of life or the most advanced. Like the earliest forms of life, they are often self-assembling: somehow creating themselves out of a material murk. How does this happen? How does disorganized matter become organized, highly effective matter in violation of the laws of thermodynamics? It is wondrous: segments of genetic code, through some form of force, gather and assemble proteins to create a vehicle for themselves. Where does this energy come from? What is moving the proteins? How does any of this happen? What the hell is life? What's more advanced, if life is about transferring genetic code? slow, heavy, sentient, rarely reproducing life forms, or lethally effective machines built for one purpose only -- to replicate genetic code? Who wins the cosmic game of Life?

simulation of viral capsid self-assembly

Viruses are one of those things in the universe that just make you wonder what the point of anything is.

Scientists have begun to use viruses to assemble materials on a molecular level.

Scientists at MIT have recently been able to use viruses to create metallic wires, and they have the potential to be used for binding to exotic materials, self-assembly, liquid crystals, solar cells, batteries, fuel cells, and many other interesting areas.

The essential idea is to use a virus with a known protein on its surface. The location of the code for this protein is in a known location in the DNA, and by randomizing that sequence it can create a phage library of millions of different viruses, each with a different protein expressed on its surface. By using natural selection, one can then find a particular strain of this virus which has a binding affinity for a given material.

Intriguingly, some researchers are exploring deploying the virus as a weapon against disease. This seems weird and fantastic.

Viro-therapy (Using viruses as treatment against various diseases) is not a new idea. In cancer therapy for example it was recognized as early as the mid 20th Century, when a number of physicians noticed an interesting phenomenon: some of their patients, who suffered from cancer and had an incidental viral infection, or subjected to vaccination, were now improving, experiencing a remission from their symptoms. In the 40's and 50's, studies were conducted in animal models to evaluate the use of viruses in the treatment of tumors, and in 1956, one of the first human clinical trials with oncolytic viruses ("onco" meaning cancer, "lytic" meaning "killing") was conducted in patients with advanced-stage cervical cancer. Nevertheless, systematic research of this field was delayed for years, due to lack of more advanced technologies. In recent years the research in the field of oncolytic viruses began to move forward more quickly and Researchers are trying new ways to use viruses for the therapeutic benefit of mankind.

In 2006 Researchers from the Hebrew University have succeeded in isolating a variant of the Newcastle disease Virus (NDV-HUJ), which usually affects birds, in order to specifically target cancer cells [2]. The Researchers tested the new Viro-therapy on Glioblastoma multiforme patients and achieved promising results for the first time